Exhaust from engines such has diesel engines are filtered for particulate matter. A clogged filter can reduce the performance of the engine. Filters are often changed or cleaned based on a time frame measured in engine running time, miles driven or time as measured by the calendar. Such time intervals can result in clean filters being changed or cleaned and dirty as clogged filters remaining in service until the next time interval.
Accordingly, it is desirable to provide a method and apparatus that determines the actual condition of the filter.